Device for preventing a free catheter flow

ABSTRACT

A catheter for connecting an administering device to an administering needle, the catheter including a catheter wall, a flow region limited by the catheter wall, and at least one catheter portion at which at least one partial piece of the catheter wall abuts at least one other partial piece of the catheter wall to releaseably block or obstruct the flow of a medium through the catheter, wherein the flow is unblocked or opened when the medium exhibits a pressure above a predetermined blocking pressure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 12/644,446 filed on Dec. 22, 2009, which is a continuation of International Patent Application No. PCT/EP2008/004281 filed on May 29, 2008, and which claims priority to European Application No. 07 111 4235, filed on Jun. 29, 2007.

BACKGROUND

The present disclosure relates to devices for delivering, injecting, infusing, administering or dispensing a substance, and to methods of making and using such devices. More particularly, it relates to a device for preventing a flow through a catheter, and more particularly to a catheter formed such that a flow of a fluid through the catheter due to a hydrostatic pressure of the fluid or liquid flowing through, channeled in or conducted through the catheter is blocked or prevented. The present disclosure also relates to a system comprising such a catheter and an administering device, e.g. an infusion pump.

Known infusion systems store a drug to be administered in a container, usually an ampoule, in which a carrier fluid with the drug dissolved in it—referred to in the following simply as the drug fluid—is situated between a movable stopper and a container outlet. One end, which may be thought of as the rear end, of a catheter is connected to the container outlet. A needle, which is introduced into the human or animal body to administer the drug fluid, is placed on the other, front, end of the catheter and in most cases remains there for an administering period which is often several days, wherein if the container with the drug fluid is situated at a greater height than the front end of the catheter and/or the needle, there exists the danger, if the difference in height between the container and the front end of the catheter is large enough, of the container gradually emptying itself due to the force of the column of fluid.

In insulin therapy using portable infusion apparatus, for example pump apparatus, the catheters used can exhibit lengths of more than 1 m. If the apparatus, including the container, is arranged vertically above the user, for example at night or when showering, a hydrostatic ground pressure of about 0.1 bar is generated, if no other effects—for example friction losses, discharge effects or capillary action—are taken into account in addition to the purely static pressure due to the inherent weight of the drug fluid, and if the density of water is assumed for the drug fluid.

To prevent any undesirable discharge due to the pressure of the column of fluid, the wall friction between the stopper, which is accommodated in the container such that it can slide freely, and the container wall could be increased; however, this would incur other disadvantages. Another solution would be to fix the stopper to the driven member of an infusion pump, such that the stopper prevents the surface of the fluid from dropping in the container and so prevents it from emptying itself. Known systems involving screwing the stopper to the driven member. This, however, increases the cost of the apparatus. Also, this solution cannot be used with prefabricated ampoules, since the stopper is not prepared for a screw connection.

International application WO 97/02059 relates to an infusion pump comprising a pump casing and a safety valve which is intended to prevent delivery of the drug from being caused by gravity alone. The connecting casing of the pump is detachably fastened to the pump casing. Also, its upstream end is connected to a sack-like drug reservoir via a catheter and an inlet connector.

International application WO 95/16480 discloses an infusion device comprising a drug container, a catheter leading away from it, a clamp arranged on the catheter, a pump connected to the catheter, another catheter leading from the pump to the patient, and a safety valve arranged in said other catheter. By means of the clamp for the first catheter and the safety valve, the intention is to prevent the drug fluid from being undesirably conveyed due to gravity.

EP 0 882 466 A2 discloses a device for administering, in particular infusing, a drug fluid in doses, comprising a container from which the drug fluid is displaced in doses through an outlet when a stopper is advanced, to administer it, and comprising a catheter which is connected to the container at the outlet, wherein the front end of said catheter facing away from the outlet is or can be connected to an administering needle, wherein a valve is arranged between the outlet and the administering needle in a flow cross-section of the drug fluid, and the valve only allows a flow toward the front end of the catheter when the fluid pressure acting in this direction is greater than a pressure bearing on the valve as a result of the inherent weight of a column of fluid in the device, to prevent the container from emptying itself.

SUMMARY

Disclosed hereinafter are various embodiments to a catheter and a system which comprises the catheter and an administering device which prevent a drug fluid or substance to be dispensed through the catheter from being dispensed or discharged in an uncontrolled manner.

In one embodiment, a catheter for connecting an administering device to an administering needle is disclosed. The catheter may include a catheter wall, a flow region limited by the catheter wall, and at least one catheter portion at which at least one partial piece of the catheter wall abuts at least one other partial piece of the catheter wall to releasably block or obstruct the flow of a medium through the catheter, wherein the flow is unblocked or opened when the medium exhibits a pressure above a predetermined blocking pressure.

In one embodiment, a catheter in for connecting an administering device, for example an infusion pump which is known in its own right, to an administering needle which can be included in a so-called infusion set, is disclosed and comprises a catheter wall which is provided as a continuous one-part wall of a tubular or flexible tubular catheter made from an elastic material. The inside of the catheter wall (or walls) limits or defines the flow region of the catheter, through which a drug fluid or substance, dispensed from an infusion pump, is conveyed to an administering point and to an administering needle. In one embodiment, the catheter comprises at least one catheter portion at which at least one partial piece of the inner wall of the catheter abuts at least one other partial piece of the inner wall of the catheter, to automatically block or obstruct the flow through the catheter, wherein the flow is re-enabled and the catheter opened when the fluid being guided in the catheter exhibits a pressure above a predetermined minimum pressure of, for example, more than 0.1 bar or more than 0.2 bar.

In some embodiments, providing a catheter portion comprising an inner wall of the catheter which, in its normal state without the application of a predetermined minimum pressure of the fluid being guided by the catheter, is automatically deformed—for example by correspondingly shaping the catheter wall and/or using specific, for example elastic, materials or by applying an external force such as for example attaching one or more clamping pieces—such that a flow through the catheter is only possible once a predetermined minimum pressure of, for example, more than 0.1 bar is exceeded, has the advantage that additional valves do not have to be provided at the end of the catheter or in the catheter to control and/or prevent a free flow. A self-blocking catheter can thus be designed very simply and also prevent incorrect use, since additional valves do not have to be connected and therefore also cannot be forgotten when the catheter is used.

In some embodiments, a catheter may comprise two or more catheter portions which are, for example, spaced apart from each other in the longitudinal direction, i.e. along a length of, and/or in flow direction of the catheter, to form two or more zones to prevent a free flow through the catheter when a pressure below the predetermined minimum pressure is applied. For example, two or more zones can be formed in immediate succession, within which the inner walls or surface(s) of the catheter abut each other, wherein preventing a free flow at a pressure below the predetermined minimum pressure can be realized by an individual zone, e.g. by the inner walls of the catheter abutting each other, or by automatic sealing within an individual region or zone, or also by a number of successively arranged zones co-operating, in which the catheter walls abut each other, spaced apart from each other in the longitudinal direction of the catheter, at a number of portions and thus form a number of blocking or securing elements along the length of the catheter.

In some embodiments, the minimum pressure which has to be applied to re-open the self-blocking or self-sealing on the catheter is around at least 0.1 bar and, in some embodiments, above 0.1 bar, i.e. in the range above 0.15 bar or 0.2 bar or above 0.3 bar or 0.7 bar.

When the ampoule is biased, i.e. a minimum impact force is applied to the stopper, it may be that the fluid pressure at the outlet region of the ampoule is around a higher pressure of, for example, 0.5 bar. Accordingly, in some embodiments, the opening pressure of the catheter should be around this higher pressure, plus a safety pressure of, for example, 0.1 bar or 0.2 bar.

In some embodiments, to obstruct administering the drug in doses as little as possible, but still securely prevent discharge, the catheter is configured such that it only allows the flow toward the front end of the catheter when the fluid pressure in this direction (the flow direction) exceeds the maximum possible pressure of the column of fluid, in some embodiments, multiplied by a safety factor. Since, in the present case, the valve is being used in the medicinal field, the safety factor may correspond to the value 3. For a maximum catheter length of about 1 m and a negligible column of fluid in the container, the maximum fluid pressure at the free end of the catheter measures about 0.1 bar, such that in this case, the catheter is configured such that it only opens when the fluid pressure exceeds 0.3 bar. These are also the dimensions for an exemplary use in a portable infusion pump.

In some embodiments, the catheter is self-closing or self-blocking below the aforementioned blocking pressure or minimum pressure and can thus effectively prevent a substance or drug fluid from unintentionally flowing through it due to the pressure of the column of fluid within the catheter.

In some embodiments, a catheter comprises regions or portions in which the walls of the flexible tube are biased against each other. This can, for example, be achieved by only one partial piece being biased toward another, for example opposing inner wall of the catheter in the circumferential direction of the catheter, or by two regions of the catheter wall which oppose each other being biased toward each other, to abut each other when there is a lack of pressure in the medium being guided in the catheter, such that the flow is blocked below the mentioned minimum pressure which enables a flow. A partial piece of the catheter or a region of the catheter wall can, for example, be biased by using an elastic material which is provided on or in the catheter or as a part of the catheter wall, such that one or more catheter walls are biased in a direction which reduce and, in some embodiments, completely seal the flow region, i.e. an opening within the catheter.

Alternatively or additionally, an external element, for example a clip or clamping device, which is formed as a suitably-shaped, e.g. U-shaped, spring element can generate an external force which acts on the outer wall or walls of the catheter, to press together the catheter between or by the clip element or spring element. When the predetermined minimum pressure is applied, for example generated by an infusion pump, a fluid passing through the catheter can press the external element apart far enough to enable a flow through the catheter, which is limited in accordance with the pressure being applied or which is unobstructed.

In some embodiments, the catheter can also be reshaped by a production process or by an external element, such as a clamping element, such that the catheter is not annular in cross-section like known catheters but rather exhibits a different shape for blocking a flow. For example, in some embodiments, a catheter may have the shape of a flat flexible tube in which the wall halves abut each other and can thus prevent a flow at a low pressure.

Furthermore, in some embodiments, it is also possible for the catheter to be embodied so as to be bent or sharply bent and for this bent or sharply bent shape to be realized either by the catheter materials, by catheter geometry used, and/or by an external element such as a clamping piece which holds the catheter in a bent or sharply bent shape.

In another embodiment, a system comprising a catheter such as has been described above and an administering device, e.g. an infusion pump, for administering a drug fluid in doses is disclosed. The drug fluid is contained in a container from which it is displaced, to be administered, in doses by advancing a stopper which is movably accommodated in the container toward a container outlet. The rear end of a catheter such as has been described above can be connected directly to the outlet of the container, where an outlet piece and/or outlet support for connecting a catheter is provided. The catheter is usually a flexible tubular catheter. It would, however, be equally possible to use a rigid catheter comprising elastic partial pieces. The front, free end of the catheter is or can be connected to a needle for administering the drug. The term “Administering” is understood to mean both infusing and injecting and/or a combination of the two types of administering. Thus, some embodiments are intended to be used in infusion devices and/or infusion apparatus, which may be portable pump apparatus for insulin treatment.

In some embodiments, the self-blocking element or partial piece of the catheter is arranged between the container outlet and the needle for administering the drug, in a flow cross-section of the drug fluid. The catheter is dimensioned such that, to prevent it from emptying itself, it only allows a flow toward the front end of the catheter when the fluid pressure acting in this direction is greater than a pressure bearing on the self-blocking portion as a result of the inherent weight of the column of fluid in the device. If the device is a mass-produced device, for which a whole range of catheters having different lengths are available, then the self-blocking portion is dimensioned for using the longest catheter, i.e. for the maximum possible column of fluid.

Although the self-blocking portion or the self-blocking partial regions of the catheter can in principle be placed at any point between the container outlet and/or infusion pump and the administering needle, in some embodiments the portion or region is arranged as near as possible to the outlet of the container or as near as possible to the infusion pump.

In another embodiment, a method for preventing a free flow through a catheter, wherein at least a partial region of the catheter or the catheter wall prevents the flow of a medium below a predetermined minimum pressure, and wherein the catheter is pressed open to enable the flow when the medium exceeds the minimum pressure is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view onto a partial piece of an embodiment of a catheter comprising a clip;

FIG. 1A is a sectional view along the line A-A in FIG. 1;

FIG. 1B is a sectional view along the line B-B in FIG. 1;

FIG. 2 depicts an embodiment of a self-blocking catheter comprising two blocking regions;

FIG. 2A is a cross-sectional view along the line A-A in FIG. 2;

FIG. 3 is a schematic representation illustrate a working principle of an embodiment;

FIG. 4 depicts an embodiment comprising a number of successively arranged, sharply bent regions; and

FIGS. 5A, 5B, and 5C depict another embodiment of a self-blocking catheter comprising a separate pressure element.

DETAILED DESCRIPTION

With regard to fastening, mounting, attaching or connecting components of the present invention, unless specifically described as otherwise, conventional mechanical fasteners and methods may be used. Other appropriate fastening or attachment methods include adhesives, welding and soldering, the latter particularly with regard to an electrical system of the invention, if any. In embodiments with electrical features or components, suitable electrical components and circuitry, wires, wireless components, chips, boards, microprocessors, inputs, outputs, displays, control components, etc. may be used. Generally, unless otherwise indicated, the materials for making embodiments of the invention and/or components thereof may be selected from appropriate materials such as metal, metallic alloys, ceramics, plastics, etc. Unless otherwise indicated specifically or by context, positional terms (e.g., up, down, front, rear, distal, proximal, etc.) are descriptive not limiting. Same reference numbers are used to denote same parts or components.

FIG. 1 shows a first embodiment of a blocking valve 2 which is formed on a catheter 1, directly on or in the flexible catheter tube and in the vicinity of the outlet point of a pump (not shown). The blocking valve 2 is configured such that it blocks or prevents flow when an interior pressure of the flexible tube or a pressure of the medium being guided in the flexible tube 1 is 0.1 bar or less, and opens at higher pressures and allows a flow through the flow region 1 b of the catheter 1.

The first embodiment of the catheter 1 shown can, for example, be obtained by reshaping the catheter or flexible tube in the region of the valve 2 by a thermal reshaping method, wherein the annular or tubular cross-section of the catheter 1 is reshaped in the region of the valve 2 into a flat flexible tube, as shown in the sectional view in FIG. 1A, such that the wall halves 1 a of the catheter 1 abut each other and can thus prevent a flow when a low interior pressure is being applied. If the pressure of the medium being guided in the catheter 1 rises above a predetermined minimum pressure of, for example 0.1 bar, the inner wall 1 c of the catheter is pushed open and the valve 2 is opened, such that a flow through the catheter 1 is possible.

As can be seen from FIGS. 1A and 1B, the valve 2 can be fitted with a clip 3 which is formed as a U-shaped spring element and comprises pressing pieces 3 a and 3 b. The clip 3 is arranged around the catheter 1 and can bias the catheter halves and therefore the inner walls 1 c of the catheter against each other via its clamping force. By using the clip 3, it is possible to set a defined blocking force or blocking pressure. The greater the force with which the clip 3 presses the inner walls 1 c onto each other, the greater the minimum pressure of the medium which has to be applied to enable a flow through the catheter 1.

If such a catheter 1, comprising one or more valves 2 successively arranged in the longitudinal direction of the catheter 1, is connected to an administering device, for example an infusion pump, the catheter 1 is connected to a reservoir for a substance or medium to be administered. Usually, as depicted by FIG. 3, a stopper 5 is inserted into the reservoir or an ampoule by an infusion pump, such that the interior pressure in the ampoule is increased and a substance contained in the ampoule is dispensed from a dispensing opening of the ampoule. This causes a rise in pressure in the connected catheter 1, which ensures that the catheter walls 1 a, which are biased against each other, are pushed open and that a desired amount of the substance, such as for example insulin, can thus be dispensed to a patient. As soon as the desired amount of the substance has been administered, and the stopper 5 of the reservoir is at rest again, the valve 2 closes due to the force of the clip 3 which presses the catheter 1 together again, automatically. The opening pressure for the valve 2 is thus set or defined by the biasing force of the clip 3.

FIG. 2 shows a second embodiment of a catheter 1 in accordance with the present invention, comprising two valves 2. The two valves 2 are arranged in two zones spaced apart from each other in the longitudinal direction of the catheter 1, i.e along the length of the catheter, and comprise catheter walls 1 a which are respectively biased against each other, wherein one catheter wall 1 a of a first side, shown on the left in FIG. 2A, is biased toward the second side (in the drawing, downwardly), such that the inner walls 1 a of the catheter abut each other and prevent a flow of a medium when a predetermined minimum pressure is not being applied. In the region of the second valve, shown on the right, the bias relative to the first valve is reversed, i.e. the opposing second side is biased toward the first side, such that the desired valve blocking effect occurs.

Each bias of a catheter wall 1 a can thus be regarded as an aperture. If a number of apertures are arranged in series, such as illustrated by embodiment shown by FIG. 2, the overall difference in pressure is divided into stage differences in pressure, such that the drop in pressure per valve zone can be reduced. By reducing the overall difference in pressure, the closing force per valve zone can then be reduced and the functional reliability of the overall valve, formed from a number of valve zones, can thus be increased.

In accordance with another embodiment of the present invention, a valve function using a catheter 1 can be achieved by moving the catheter 1 into a sharply bent region using a defined path-force element (spring). When the pressure rises, for example between 0.5 and 0.8 bar, the catheter 1 is released from the sharply bent region and so releases the flow.

FIG. 3 schematically shows an ampoule comprising a stopper 5 which can be shifted within it in the direction of the arrow and using which a substance contained in the ampoule can be dispensed from a dispensing opening to the catheter 1 connected to the ampoule. If, for example, the difference in height between the lower and upper end of the catheter 1 measured one meter, then a partial vacuum of 0.1 bar would be applied at the upper end of the catheter 1, which could cause a substance to be unintentionally dispensed from the ampoule in an uncontrolled manner, solely due to the hydrostatic pressure generated by the column of fluid in the catheter 1.

In some embodiments, a valve is arranged in the upper region of the catheter, such that a partial vacuum of 0.1 bar in relation to a relative exterior pressure of 0 bar causes the catheter walls 1 a to be automatically pressed together. If the catheter walls 1 a are elastic, the partial vacuum in the upper catheter portion can therefore be utilized such that in the event of a hydrostatic pressure distribution in the catheter, the valve is automatically closed.

If the above-described catheter 1 is used, then it is possible to prevent a substance from being unintentionally dispensed from the ampoule 4 through the catheter 1.

In some embodiments, a number of sharply bent regions 1 d can also be successively arranged, as shown in FIG. 4, wherein a catheter or flexible tube 1 is accommodated in a clamping piece or clip 3 which can consist of an upper part 3 c of the clamping piece and a lower part 3 d of the clamping piece, which can be connected to each other. The catheter 1 is inserted into the catheter guides, which are, for example, formed by a number of mutually parallel partition wall pieces 3 e, such that the catheter 1 is held meandering, or snaking or winding, in the clamping piece 3, wherein linear regions of the catheter 1 are parallel to each other, separated by the wall pieces 3 e, wherein a sharply bent region 1 d is provided in each region in which the catheter 1 transitions from one guide, formed by two adjacent wall pieces 3 e, to the next guide. FIG. 4 shows the open-catheter state, in which the sharply bent regions 1 d are open, due to an applied pressure of, for example, more than 0.7 bar, and so enable a flow of a medium through the catheter 1. If a pressure below 0.7 bar is being applied, the catheter 1 is deformed in the sharply bent regions 1 d, such that a medium is prevented from passing through the catheter 1.

The clamping piece 3 can, for example, be formed to be rigid, such that when the pressure of the medium being guided in the catheter 1 rises above 0.7 bar, a flow is enabled solely by the deformation of the catheter 1. Alternatively, the clamping piece 3 can also be formed to be elastic or flexible, such that when the pressure of the medium being guided in the catheter 1 rises, the clamping piece 3 is deformed or expanded and so releases the flow for the fluid being guided in the catheter 1.

Although the clamping piece 3 could in principle be formed in one piece, in some embodiments it is formed—to more easily insert the catheter 1—from two partial pieces 3 c and 3 d which can be placed onto each other or connected to each other, after the catheter 1 has been inserted into the clamping piece 3 d in the manner shown in FIG. 4, such that the catheter 1 exhibits a number of successive sharply bent regions 1 d on two opposing sides of the clamping piece 3.

FIG. 5A shows another embodiment of a blocking mechanism for a catheter 1, wherein a catheter blocking valve can be both integrated into the catheter 1 and formed as a separate valve piece which can be inserted between two catheter pieces 1. In the embodiment shown in FIG. 5A, a valve base body 4 made from a thermoplastic elastomer (TPE) can be seen which is formed in the shape of a disc or plate and is flat. The body 4 has been inserted between two catheter pieces 1, wherein the body 4 has been placed onto the catheter pieces 1 in the region of a fusing zone 4 a and connected or fused to the catheter pieces 1, so as to be an integrated part of the catheter. A sealing or covering element 4 b, in the form of a film which is likewise formed from a thermoplastic elastomer, is placed onto the valve base body 4 and can be formed double-layered and from a different material than the valve base body 4. The film 4 b is connected to the valve base body 4 in the region of a fusing zone 4 c.

A bent clip 3 formed from spring steel may be slid or placed onto the valve base body 4 connected to the film 4 b, in a similar way to the embodiment described with respect to FIG. 1. The clip comprises two mutually opposing pressure surfaces 3 f and 3 g, such that the upper pressure surface 3 f can press onto the film 4 b and the lower pressure surface 3 g can press onto the lower side of the valve base body 4. FIG. 5C is a top view onto the clip 3 which is shown in a lateral view in FIG. 5B.

If a pressure of, for example, less than 0.7 bar is being applied to the medium being transported in the catheter 1, then the film 4 b is pressed into the valve base body 4 or the valve base body 4 is pressed together with the film 4 b, such that a flow of a medium cannot occur. If the pressure of the medium rises above 0.7 bar, then the clip 3 is pressed or urged apart by the pressure of the medium, i.e. the pressure surfaces 3 f and 3 g are urged away from each other enabling a flow of the medium.

The blocking pressure of the valve shown in FIG. 5 can be altered by the configuration of the clip 3, and/or by its manufacture, deformation and material constants or processing, such that the valve can also open at a lower pressure of, for example, 0.1 bar or 0.2 bar or at a higher pressure of, for example, 1 bar or above.

Embodiments of the present invention have been presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms and steps disclosed. The embodiments were chosen and described to illustrate the principles of the invention and the practical application thereof, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth they are fairly, legally, and equitably entitled. 

1. A catheter for connecting an administering device to an administering needle to administer a medium, the catheter comprising: a longitudinally extending, continuous catheter wall defining an opening through which the medium is conveyed to the needle from the device, said wall having a number of free flow zones in which the medium flows freely within the catheter and a self-blocking zone connecting, in a flow direction of the catheter, a distal end of one free flow zone with a proximal end of a next free flow zone, wherein the catheter in the self-blocking zone is wider in cross-section than in the free flow zones, and wherein in the self-blocking zone at least one partial piece of an inner wall of the catheter wall in the circumferential direction abuts at least one other partial piece of the inner wall to block a flow of the medium through the self-blocking zone, wherein the partial pieces of the inner wall are separated when the medium exhibits a pressure above a predetermined blocking pressure, thereby permitting the flow, and automatically return to abut one another when the pressure exhibited by the medium is below the predetermined blocking pressure.
 2. The catheter according to claim 1, wherein the blocking pressure is around at least 0.1 bar or above.
 3. The catheter according to claim 1, wherein the blocking pressure is one of approximately 0.2 bar, approximately 0.3 bar or approximately 0.7 bar.
 4. The catheter according to claim 1, wherein in the self-blocking zone the at least one partial piece of an inner wall of the catheter wall comprises a different elasticity, a different material or a different thickness relative to the at least one other partial piece of the inner wall.
 5. The catheter according to claim 1, further comprising a clamping device for deforming the catheter such that the catheter is flattened in the at least one partial region.
 6. The catheter according to claim 1, wherein the at least one partial piece of the inner wall abuts the at least one other partial piece of the inner wall via a clip having an upper part and a lower part pressing on respective pieces of the inner wall.
 7. The catheter according to claim 1, wherein in the self-blocking zone the at least one partial piece of an inner wall of the catheter wall forms as base body and the at least one other partial piece of the inner wall forms a covering element to the base body.
 8. The catheter according to claim 7, wherein the free flow zones of the catheter are connected only to the base body.
 9. The catheter according to claim 7, wherein in the base body comprises a different material or a different thickness relative to the covering element.
 10. The catheter according to claim 7, wherein the base body and the covering element is made from a thermoplastic elastomer.
 11. The catheter according to claim 7, wherein the covering element is in the form of a film.
 12. The catheter according to claim 7, wherein the covering element abuts the base body via a clip pressing together the covering element and the base body.
 13. The catheter according to claim 12, wherein the clip comprises two mutually opposing pressure surfaces.
 14. The catheter according to claim 12, wherein the clip is formed from spring steel.
 15. The catheter according to claim 1, wherein the catheter comprises a second self-blocking zone having a cross-section wider than in the free flow zones, and wherein in the second self -blocking zone at least one partial piece of an inner wall of the catheter wall in the circumferential direction abuts at least one other partial piece of the inner wall to block a flow of the medium through the second self-blocking zone, wherein the partial pieces of the inner wall are separated when the medium exhibits a pressure above a predetermined blocking pressure, thereby permitting the flow, and automatically return to abut one another when the pressure exhibited by the medium is below the predetermined blocking pressure.
 16. The catheter according to claim 15, wherein the catheter in the self-blocking zone is in the shape of a disc or plate.
 17. The catheter according to claim 15, wherein the at least one partial piece of an inner wall of the catheter wall abuts the at least one other partial piece of the inner wall via automatic material deformation.
 18. The catheter according to claim 15, wherein the blocking pressure of each self-blocking zone divides the overall difference in pressure of the medium into stage differences in pressure.
 19. The catheter according to claim 15, wherein the blocking pressure of each self-blocking zone is around at least 0.1 bar or above.
 20. The catheter according to claim 15, wherein the blocking pressure of each self-blocking zone is one of approximately 0.2 bar, approximately 0.3 bar or approximately 0.7 bar. 